1. Field of the Invention
The present invention relates to an apparatus and a method for translating IP (Internet Protocol) addresses used on an IP network, e.g. IPv4 (IP version 4) telecommunications network, in which a global address may be used in common with a plurality of access nodes, thereby suppressing the global address resource from going to exhaust.
2. Description of the Background Art
In the conventional IP network, a manner of sharing a global address with several nodes has been established by mapping a node group having plural private addresses onto the port number included in information of a Layer 4 header. For instance, there are generally used the NAT (Network Address Translation) and NAPT (Network Address Port Translation) manners as disclosed in RFC791, “Internet Protocol”, September 1981, and RFC3022, “Traditional IP Network Address Translator (Traditional NAT)”, January 2001, respectively. In addition, Japanese patent laid-open publication No. 2006-5754 discloses techniques utilizing the NAT manner.
In recent years, a rapid spread of various telecommunications networks causes the IPv4 address resource, to be allocated as global addresses, to exhaust. As a result, the necessity of IPv6 (IP version 6) is more increased and popularization of IPv6 is more required.
In fact, however, almost widely popularized terminal devices can work only under the IPv4. Taking suppression of charges on users into account, common carriers should not easily recommend the users to replace their devices with ones available for IPv6.
Therefore, in a transitional period when networks are shifted from the IPv4 environment to the IPv6 environment, the networks will possibly have to work under the IPv6 environment besides the IPv4 environment. In the future also, the IPv4 addresses will possibly continue to be utilized to maintain their important position.
Now, a network art is required which uses the NAT in access control to the Internet to allocate private IPv4 addresses to end users.
With the conventional NAT manner, however, since an IPv4 global address has to be used in common with plural users, available port numbers may be restrictive. For example, if 65,535 ports are shared with plural, e.g. 2,000, users, only 25 to 30 sessions are available for each user.
For example, when acquiring image data, use is generally made of multi-session access in which a session is used per image so that more images to be acquired cause more sessions required. In case of acquiring images around San Francisco, United States, on the website of Google (trademark) Maps, for example, images can be displayed ordinarily with 30 sessions. However, if only 15 sessions are used, approximately half of the images may be displayed. Moreover, if only five sessions are used, an error message “server is not found” may be displayed. For other websites, such as Yahoo (trademark), ITunes (trademark) and Rakuten (trademark), approximately 10 to 20, 230 to 270 and 90 sessions may respectively be required.
In the IPv4 environment, in order to make a smooth use of web applications thus using a multi-session access to work by transmitting and receiving a large amount of information within a short period of time, a carrier-grade address translation system will be necessary.
In addition, the traditional address translation technology, such as NAT, is able to efficiently utilize global addresses, but is not able to deal with modern applications for peer-to-peer or end-to-end communications, such as VoIP (Voice over IP) communications. There is therefore a problem that applications are restrictively available.